Many individuals desire a “bright” smile and white teeth, and consider dull and stained teeth cosmetically unattractive. Thus, there is a desire for whiter teeth and one means to achieve whiter teeth is the use of tooth whitening products.
Teeth can become discolored by foods, drinks and tobacco use. Dental stains can be classified as either extrinsic, which occur on the outer surface of teeth, or intrinsic, which occur below the surface of enamel. Most abrasive containing toothpaste remove extrinsic stains. Hydrogen peroxide (H2O2) can bleach both extrinsic and intrinsic stains and so provides fast and superior whitening efficacy. The peroxide can bleach the teeth, remove stains, and kill cariogenic bacteria. However, peroxide compounds are highly reactive, and consequently difficult to formulate. Moreover hydrogen peroxide can spontaneously decompose to form oxygen gas (O2) and water. The off-gas accumulation can be problematic as in storage, dentifrice containers may bloat, burst or leak, and the remaining formulation will not have enough peroxide remaining to clean and whiten teeth effectively.
To alleviate this, some dentifrices initially comprise very high levels of peroxide, which decomposes over time, so that the exact amount of peroxide delivered on application is variable and largely depends on how long and under what conditions the dentifrice has been stored. In alternative methods, the pH of the composition is decreased to an acidic range in order to increase H2O2 stability (see, for example U.S. Pat. No. 4,839,156).
Current oral care market products do not adequately address off-gassing resulting from hydrogen peroxide decomposition. Accordingly, there is a need for oral compositions having stable hydrogen peroxide formulations.